Limit users of a group to only create content for that group

Is there any way to automatically force content created by a groups member to only create for that particular group?

For instance:
I have two departments (groups)
G1
G2
They have separate users.
When they create content, I want to limit access to that content automatically to only be shown to respective department. Frontend and backend posting for this.

Or will I have to build a function for this?